1. Field of the Invention
The apparatus of this invention resides in the area of shot blast machines utilized for cleaning drums and more particularly relates to a workpiece pass-through system for cleaning open-ended drums, barrels and the like by shot blast wheels positioned in the apparatus of this invention.
2. Description of the Prior Art
It is often necessary to clean large numbers of open-ended and closed-end drums typically of the 30-gal, 55-gal and 85 gal size which drums are often utilized for the transportation of foodstuffs or other materials. Thorough cleaning of the drum is especially necessary if the drum is to be reused.
To clean such drums, shotblast techniques have been employed with the drum mounted on a conveyor system and indexed through a machine in a horizontal plane with the drum lying on its side. The horizontally-oriented drums in such machines are moved by drag chains or pushrods and are spun in the blast area on wheels positioned in the conveyor system. A minimum of three blast wheels are provided with the first positioned to propel shot at the front open end of the drum; the second, at the rear end; and the third, on the top of the drum as it passes through the machine. A problem with machines of this type having blast wheels positioned to propel shot in a horizontal plane to the drum opening is that if the horsepower of the wheel exceeds approximately 20 hp, the force of the abrasive blast directly into the drum tends to blow the drum off the roller conveyor system which occurrence disables and jams the entire cleaning machine.
To try to overcome this problem when cleaning drums in the conventional manner in horizontal drum array systems, a pair of guide rails between 6"-12" in height have been provided extending the entire length of the machine which guide rails are disposed at each end of the drum and which guide rails contain and form a channel for the drums to pass therein as they are indexed through the machine during the blast cleaning process. However, if the force of the shot blast stream is too great, these guide rails will not prevent the drums from being blown out over the guide rail due to the drum's relatively light weight.
A further problem that arises in systems in which the drums are horizontally arrayed on their sides is that even though the drums are rotating, abrasive material builds out of the drums because such abrasive material cannot fully drain out of the drums because the sides of the drums are always horizontal. This abrasive material buildup in the drum causes a blinding action to further cleaning since further particles blasted within the drum cannot strike the portion of the drum covered by abrasive material. This abrasive buildup prevents a thorough cleaning of the covered area especially at the chime of the drum where the bottom of the drum meets the sides.